Will a GOP Senate Be the Final Casualty of the Tea Party?

If this new Public Policy Polling survey is any indication, Rep. Mike Castle -- longtime congressman and fixture of the Delaware GOP -- might be the latest Republican pol to lose his bid for his party's Senate nomination. Over the last month, Castle's popularity with Delaware Republicans has taken a sharp turn; in early August, 60 percent of Delaware Republicans had a favorable view of Castle. By now, Castle's favorability has dipped to 47 percent, while his negatives have risen to 43 percent. Fifty-five percent of Delaware Republicans think Castle is too liberal -- although he's voted with his GOP colleagues in the House 87.3 percent of the time in the 111th Congress -- and only 37 percent think he's "just right" for the party nomination.

Who stands to gain from Castle's abrupt change in fortune? Tea Party candidate Christine O'Donnell, who has earned endorsements from Sarah Palin, Sen. Jim DeMint and the National Rifle Association, in addition to receiving buckets of money from the Tea Party Express, which has used this contest to open another front in its seemingly internecine war with the GOP establishment. According to PPP, O'Donnell leads Castle 47 percent to 44 percent, with 8 percent of voters undecided. State Republicans have made a big push to discredit O'Donnell as unqualified to hold office, but she might have enough support among Republican primary voters to push Castle out of the race, which would turn a near certain GOP pickup into a near certain Democratic hold.

I don't see the Tea Party as harming Republican prospects in the House -- if anything, Tea Party-driven enthusiasm has greatly helped the GOP -- but I also don't think it's a stretch to say that the Tea Party's enthusiasm for fringe candidates could cost the GOP control of the Senate. To win both chambers in November, Republicans need to win 10 seats. That was always unlikely, but recently, it looked possible. Now, however, with an unpopular Tea Party candidate in Nevada and a potential Tea Party candidate in Delaware, it's trending toward impossible.